It is frequently desired to reduce the circumference or size of a finger ring so as to make it fit the finger of a new owner or wearer. A short span is cut out of the hoop and the butt ends are then brought together and secured as by metal-to-metal sealing. However, when sawing through the band, the path of the saw blade may deviate from a true radial cut so that the severed end may slant in either direction and thus produce a non-conforming butt end, as well as a somewhat greater or lesser open-span than initially calculated or desired. In addition, sometimes with softer metals or alloys an inadequately supported length may bend or crumble in the course of severance; one result is that an entire band must be reconstituted. Beyond this, is the recurrent problem of trying to visually transfer a desired severance length to the workpiece, or alternately maintaining a mensuration guide along the clamped ring.